Tiny insects, big damage

Published 5:28 pm, Friday, June 3, 2011

FINCH 0604 Spider Mites
Speckled leaves on tomato plants indicate damage from spider mites. The pests are prevalent in hot, dry weather, and they can be difficult to eradicate.
Credit: Courtesy Forrest W. Appleton less

FINCH 0604 Spider Mites
Speckled leaves on tomato plants indicate damage from spider mites. The pests are prevalent in hot, dry weather, and they can be difficult to eradicate.
Credit: Courtesy Forrest W. ... more

Tiny insects, big damage

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Spider mites are among the most destructive garden pests, and they also are among the most difficult to control. Because of the weather, they are prevalent in gardens this year.

Spider mites are organisms the size of a pinhead that live by sucking juices from plants. In many situations, the damage becomes so serious that the plant does not have the vigor to grow, bloom or produce fruit. Tomatoes are especially vulnerable.

On tomatoes, spider mite damage is obvious when leaves change from lush green to a speckled, dusty green. In advanced stages of infestation, mites produce webbing on leaves and stems.

Although a number of insecticide labels claim to control spider mites, most are not very effective.

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The reality is that complete control is not likely. In hot, dry weather, gardeners have to be content with slowing down spider mite population growth.

Seaweed extract is one control. Spray weekly with a solution diluted in water at the rate of 2 tablespoons per gallon until mites appear and then apply twice a week. Direct the spray under the leaves where the spider mites live.

Research indicates the spray slows spider mite population growth, but researchers are not sure why. Chemicals in the extract may inhibit reproduction, or they may toughen the leaf surface to the point mite feeding success is reduced.

Apply the spray in the morning or evening but never in the hot sun to minimize damage to tomato leaves and stems.

Some gardeners believe a water spray applied uniformly under the leaves will slow spider mite reproduction.

Neem oil and spinosad also may slow down the pest.

Gardeners with good eyes can usually see spider mites under the leaves of plants. If you suspect the pests, tap a leaf over a piece of white paper. Usually a few of the pests will drop onto and be visible on the paper as they scramble around.

Once spider mites become so thick that webs appear, it is time to harvest what you can and remove the infected plants from the garden. There is no treatment that will save the plant.

Discard heavily infested plants in a garbage bag so the bugs don't spread to other plants. Don't dispose of them in the compost pile unless the compost is active (hot) and far from the garden.